CN109232339B - Cleaning process for co-production of D, L-methionine, D, L-methionine hydroxy analogue and calcium salt thereof - Google Patents
Cleaning process for co-production of D, L-methionine, D, L-methionine hydroxy analogue and calcium salt thereof Download PDFInfo
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Abstract
The invention discloses a cleaning process for co-production of D, L-methionine, D, L-methionine hydroxy analogue and calcium salt thereof, which comprises the following steps: synthesizing an intermediate 2-hydroxy-4-methylthiobutyronitrile by using 3-methylthio propionaldehyde and hydrogen cyanide; preparing D, L-methionine hydroxyl analogue by using cyanohydrin under the action of inorganic acid; reacting cyanohydrin with carbon dioxide, ammonia gas or ammonium bicarbonate to synthesize 5- (beta-methylmercapto ethyl) hydantoin, reacting the obtained hydantoin with calcium hydroxide under the action of a hydrolysis auxiliary agent to hydrolyze to obtain calcium carbonate precipitate and hydrolysate, and releasing D, L-methionine from the hydrolysate by carbon dioxide to obtain crystallization mother liquor; recycling the crystallization mother liquor containing the hydrolysis auxiliary agent to the hydantoin hydrolysis step for recycling; calcium carbonate was reacted with D, L-methionine hydroxy analog to prepare D, L-methionine hydroxy analog calcium salt. The method hydrolyzes the hydantoin by matching a small amount of hydrolysis auxiliary agent with the calcium hydroxide, so that the hydantoin hydrolysis process is more economical and efficient, and the byproduct calcium carbonate is digested by co-producing the D, L-methionine hydroxy analogue and the calcium salt thereof.
Description
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to a cleaning process for co-production of D, L-methionine, D, L-methionine hydroxy analogue and calcium salt thereof.
Technical Field
Methionine (MET), also known as methionine, is an essential amino acid required by the human body and is widely used in food and health care medicines as a nutritional supplement to balance the intake of amino acids in the human body. Meanwhile, the compound feed additive is also used as an important functional nutrient to be added into animal feed, so that the growth of animals can be effectively promoted, the lean meat percentage can be improved, and the feeding period can be shortened. D, L-methionine is not synthesized in animals by itself and is taken from food. The natural feed raw materials such as soybean meal, corn and the like contain certain D, L-methionine, but the intake is still insufficient, so that the corresponding amount of D, L-methionine is required to be additionally supplemented.
Methionine hydroxy analogue (MHB), namely 2-hydroxy-4-methylthiobutyric acid, is a product of D, L-methionine molecules with amino substituted by hydroxy, and can be converted into D, L-methionine by transamination in animals, so that the methionine is a substitute for methionine, and has the advantages of economy, easy dispersion, low rumen degradation rate and the like. It can also be combined with calcium ion to obtain D, L-methionine hydroxyl calcium salt, which can supplement methionine and provide calcium source.
At present, the industrial preparation method of the D, L-methionine mainly comprises an enzymatic hydrolysis method, a biological fermentation method and a chemical synthesis method, the feed additive has huge demand, and the production cost is mainly prepared by a chemical synthesis method. The known industrial preparation process of D, L-methionine uses cyanide, methylthio propionaldehyde and ammonium carbonate or other raw materials to directly synthesize 5- (beta-methylthio ethyl) hydantoin (hydantoin for short) and then make alkaline hydrolysis and acidification so as to obtain the invented product, or uses hydrogen cyanide and methylthio propionaldehyde to firstly prepare 2-hydroxy-4-methylthio butyronitrile (cyanohydrin for short), then uses the latter and ammonium carbonate to synthesize hydantoin for making alkaline hydrolysis and acidification so as to obtain the invented product.
Most D, L-methionine synthesis manufacturers currently prepare D, L-methionine by the above process, but the processes differ in hydantoin hydrolysis and D, L-methionine acidification and separation, but can be roughly divided into the following three basic processes:
(1) process for preparing Rona-Planck
The process takes sodium cyanide, methylthio propionaldehyde and ammonium bicarbonate as raw materials to synthesize hydantoin, takes sodium hydroxide to hydrolyze hydantoin to obtain saponification liquid mainly comprising D, L-sodium methionine and sodium carbonate, and then takes sulfuric acid to acidify and separate to obtain D, L-methionine and sodium sulfate.
The process is one of the earliest D, L-methionine preparation processes, is simple, consumes a large amount of sodium hydroxide, and obtains a large amount of sodium sulfate which is difficult to separate and has low added value.
(2) Caoda calcium salt technology
The process takes sodium cyanide, methylthio propionaldehyde and ammonium bicarbonate as raw materials to synthesize hydantoin, uses calcium hydroxide to hydrolyze the hydantoin to obtain D, L-methionine sodium and calcium carbonate, separates the calcium carbonate, uses hydrochloric acid to acidify and hydrolyze filtrate, and separates the D, L-methionine. The byproduct salt is sodium chloride, calcium carbonate is calcined at high temperature to be calcium oxide for recycling, and part of calcium carbonate is directly discharged.
The process uses cheap calcium hydroxide to participate in hydrolysis, but sodium chloride and calcium carbonate are also byproducts, the calcium carbonate needs to be calcined at high temperature for recycling, the equipment investment is increased, the energy consumption is high, and the Caoda company providing the process already exits the D, L-methionine market.
(3) Degussa sylvite technology
The process uses hydrogen cyanide and methylthio propionaldehyde to synthesize cyanohydrin, the latter is then synthesized with ammonium bicarbonate to synthesize hydantoin, the obtained hydantoin is hydrolyzed by potassium hydroxide or potassium carbonate to obtain D, L-potassium methionine, carbon dioxide is introduced for acidification, and D, L-methionine is obtained by separation. The crystallization mother liquor is heated and regenerated to convert potassium bicarbonate into potassium carbonate to be recycled to hydantoin for hydrolysis, and no byproduct salt is generated.
The process adopts potassium hydroxide or potassium carbonate to hydrolyze hydantoin, all potassium salts are recycled after crystallization of mother liquor, no byproduct salt is generated, but the method also has obvious defects, all potassium salts are recycled, so the potassium salts always exist in system feed liquid, excessive potassium salts limit the acidification end point of D, L-methionine acidification crystallization, the crystal extraction rate is low, and a large amount of D, L-methionine is recycled to the hydantoin hydrolysis step in a potassium salt form. As the feed liquid is completely circulated, a large amount of D, L-methionine and sylvite are circulated back and forth along with the circulating liquid, the occurrence probability of side reaction and the accumulation rate of impurities such as formic acid, pigment and the like in the system are greatly increased, and the quality of the D, L-methionine product is influenced when the impurity accumulation rate reaches a certain limit.
Other industrialized D, L-methionine processes are optimized and developed on the basis of the three basic processes. Chinese patent CN101735125 discloses a method for preparing D, L-methionine, which comprises hydrolyzing hydantoin with alkaline potassium compound, introducing carbon dioxide into the obtained hydrolysate, and separating to obtain first crystal D, L-methionine and first crystal mother liquor; and (3) concentrating the first crystallization mother liquor, mixing with lower alcohol, introducing carbon dioxide for secondary crystallization to precipitate D, L-methionine and potassium bicarbonate, and separating to obtain a second crystallization mother liquor and a second crystallization D, L-methionine containing potassium bicarbonate. And recycling the second crystal D, L-methionine to the hydantoin hydrolysis step, and recycling the second crystal mother liquor to the second crystallization step after concentrating at 150-200 ℃. The method solves the problem of low primary crystallization rate of D, L-methionine in the sylvite process, but the D, L-methionine extracted by the second crystallization contains potassium bicarbonate, needs to be recycled to the hydrolysis step, can be extracted along with the first crystallization by crystallization again, indirectly improves the extraction rate of D, L-methionine, and the second crystallization needs to be concentrated and introduced with low-grade alcohol, has low efficiency and high energy consumption, and finally still needs to treat the second crystallization mother liquor which is always circulated.
Chinese patent CN104693082 discloses a method for preparing D, L-methionine, which comprises synthesizing hydantoin with cyanohydrin, ammonium bicarbonate or sodium cyanide, 3-methylthiopropanal and ammonium bicarbonate, then alkaline hydrolyzing and acidifying the hydantoin to pH = 3.0-6.0, crystallizing the separated D, L-methionine and a salt-containing crystallization mother liquor at 8-45 ℃; concentrating the salt-containing crystallization mother liquor at the temperature of below 60 ℃, and separating D, L-methionine from inorganic salt in the crystallization mother liquor concentrated liquor through a chromatographic column. The method realizes the complete separation and recovery of D, L-methionine and byproduct salt in the crystallization mother liquor, is suitable for treating the D, L-methionine mother liquor obtained by various processes, but has low chromatographic separation and segregation efficiency, and the D, L-methionine dilute solution and the inorganic salt solution obtained by elution separation contain a large amount of moisture, so that a large amount of moisture needs to be evaporated for realizing the recovery, and the energy consumption is huge.
Chinese patent CN102796033 (US 2015/0284323) discloses a clean preparation method of D, L-D, L-methionine, which is characterized in that hydrocyanic acid is absorbed by a crystallization mother liquor containing potassium carbonate to obtain a potassium cyanide solution, the potassium cyanide solution reacts with 3-methylthiopropanal and ammonium bicarbonate at 50-150 ℃ to prepare hydantoin, then the hydantoin solution is heated to 140-220 ℃ for saponification, the obtained saponification solution is cooled to 0-40 ℃ and is subjected to impurity extraction by an organic solvent, an extraction water phase is separated to obtain an extraction water phase, the extraction water phase is neutralized and crystallized by carbon dioxide, a D, L-methionine product and the crystallization mother liquor are obtained by separation, and the crystallization mother liquor is heated to 110-160 ℃ to remove the carbon dioxide and then is recycled to the hydrocyanic acid absorption step. The method moves the circulation of potassium salt from hydantoin hydrolysis to hydrocyanic acid absorption, reduces the amount of evaporated water of the circulation of crystallization mother liquor, and simultaneously adopts organic solvent to extract and remove reaction impurities, so that the process realizes better continuity. But after saponification, organic solution is used for extracting impurities, and D, L-methionine is in a salt state and is not extracted to remove oil-soluble viscous byproducts, but acidic impurities such as formic acid and the like are also in a salt state and cannot be removed. And the crystallized mother liquor is recycled to hydrocyanic acid absorption after decarburization to participate in hydantoin synthesis, and the mother liquor contains more complex components such as D, L-methionine, D, L-methionine dipeptide, formic acid, acrylic acid and polymers thereof, and the like, so that the occurrence probability and complexity of system side reactions are increased. Generally, the larger the recycle system, the more complex the composition, the longer the recycle cover process steps, the greater the risk of side reactions based on impurity accumulation and multiple process conditions of complex systems, the greater the impact on the yield and quality of the system product.
In summary, the current preparation process of D, L-methionine mainly faces the following problems:
(1) a large amount of alkali is consumed, and a large amount of inorganic salt with low added value is produced as a byproduct;
(2) the production process needs to evaporate a large amount of system water or generate a large amount of waste water;
(3) the material liquid circulation amount is large, and the product quality is influenced by the accumulation of system impurities;
(4) the one-time extraction rate of the D, L-methionine product is low, and the extraction cost is high;
disclosure of Invention
The invention provides a clean process for co-production of D, L-methionine, D, L-methionine hydroxy analogue and calcium salt thereof aiming at the defects of the existing D, L-methionine production process.
The process provided by the invention comprises the following steps:
(1) preparing cyanohydrin: synthesizing 2-hydroxy-4-methylthiobutyronitrile (cyanohydrin for short) by 3-methylthio propionaldehyde and hydrogen cyanide under the action of a catalyst;
(2) preparing liquid eggs: the cyanohydrin is sequentially hydrated and hydrolyzed under the action of acid, and the obtained reaction liquid is neutralized, concentrated and separated by ammonia water to obtain liquid methionine analogue (MHB) and a byproduct ammonium salt;
(3) preparing a fixed egg: the intermediate 5- (beta-methylmercapto ethyl) hydantoin (hydantoin for short) is synthesized by the reaction of cyanohydrin and carbon dioxide, ammonia gas or ammonium bicarbonate, and the hydantoin reacts with calcium hydroxide to hydrolyze in the presence of a hydrolysis aid to obtain calcium carbonate precipitate and D, L-methionine salt solution. Separating and removing calcium carbonate in the obtained hydrolysate, concentrating the filtrate, introducing carbon dioxide for crystallization, and separating again to obtain solid D, L-methionine and crystallization mother liquor containing hydrolysis auxiliary agent;
(4) cross utilization and circulation: reacting the calcium carbonate obtained in the step (3) with the liquid methionine analogue co-produced in the step (2) to prepare hydroxy calcium methionine; directly recycling the crystallization mother liquor containing the bicarbonate obtained in the step (3) or returning the crystallization mother liquor to the solid D after heating treatment, wherein the L-methionine hydrolysis step is used as a hydrolysis auxiliary agent for recycling;
the catalyst used in the step (1) for preparing cyanohydrin from 3-methylthiopropanal and hydrocyanic acid is a buffer solution, such as one or more of phosphoric acid and sodium acid phosphate or phosphoric acid and sodium hydroxide, succinic acid and sodium succinate or succinic acid and sodium hydroxide, acetic acid and sodium acetate or acetic acid and sodium hydroxide, citric acid and sodium citrate or citric acid and sodium hydroxide, and particularly preferably a sodium citrate-citric acid aqueous solution.
The acid used in the hydration and hydrolysis reaction of the cyanohydrin is sulfuric acid, hydrochloric acid or phosphoric acid, particularly preferably sulfuric acid;
preparing the liquid egg in the step (2) to obtain a byproduct ammonium salt which is one or more of ammonium sulfate, ammonium chloride, ammonium phosphate, ammonium hydrogen phosphate or diammonium hydrogen phosphate;
the hydrolysis auxiliary agent in the step (3) is one or more of sodium hydroxide, sodium bicarbonate, sodium carbonate, potassium hydroxide, potassium bicarbonate or potassium hydroxide, preferably potassium hydroxide, potassium bicarbonate or potassium carbonate, and particularly preferably potassium bicarbonate or potassium carbonate;
further, the use amount of the hydrolysis auxiliary agent in the step (3) is that the molar ratio of the metal cations of the hydrolysis auxiliary agent to the total hydantoin (hydantoin + D, L-methionine) is 0.95-1.2: 1;
further, the hydantoin in the step (3) and calcium hydroxide are subjected to hydrolysis reaction in the presence of a hydrolysis aid, and the molar ratio of the calcium hydroxide to the hydantoin is 0.8-1.2: 1;
further, the specific separation operation of the calcium carbonate and the hydrolysate in the step (3) is suction filtration, filter pressing or centrifugation, preferably filter pressing or centrifugation; the separation operation of the solid D, L-methionine crystal and the mother liquor is suction filtration, filter pressing or centrifugation;
particularly, the crystallization mother liquor containing the hydrolysis assistant in the step (4) can be directly recycled or can be recycled to the hydrolysis step after the decarburization by heat treatment.
The reaction formula of the step (1) is as follows:
the reaction formula of the step (2) is (taking sulfuric acid as an example):
the reaction of the step (3):
the reaction formula of the step (4) is as follows:
compared with the prior art, the invention has the following beneficial effects:
(1) the weak base calcium hydroxide and the potassium carbonate hydrolysis aid are matched for hydrolysis, so that the efficiency is high, the cost is low;
(2) by co-producing D, L-methionine hydroxy analogue calcium salt, the byproduct calcium carbonate is completely utilized, the energy consumption is lower than that of the recovered calcium carbonate, and no byproduct salt is discharged;
(3) the crystallization mother liquor is used as a hydrolysis auxiliary agent for circulation, so that the circulation amount is greatly reduced, and the long-term health of the system is facilitated;
(4) the dosage of the hydrolysis auxiliary agent is far lower than that of potassium salt for hydrolysis, the potassium ion content of the mother liquor with the same crystallization concentration is only 10-60% of the process content of the same potassium salt, and the methionine extraction rate is greatly improved;
(5) can realize synchronous production of D, L-methionine, D, L-methionine hydroxy analogue and calcium products thereof.
Drawings
FIG. 1 is a flow chart illustrating the process of the present invention.
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
The operation flow of the invention is as follows: adding hydrocyanic acid and 3-methylthiopropanal under the action of catalyst (citric acid and sodium hydroxide buffer salt) to obtain cyanohydrin. A part of cyanohydrin is catalyzed by inorganic acid (such as 98% concentrated sulfuric acid) to carry out hydration reaction to obtain 2-hydroxy-4-methylthio amide, the latter is supplemented with water, heated and hydrolyzed to obtain liquid methionine and ammonium bisulfate, and the liquid methionine and ammonium sulfate are obtained by separation after neutralization by ammonia water. The other part of the cyanohydrin reacts with ammonia, carbon dioxide or ammonium bicarbonate to synthesize hydantoin, and the hydantoin reacts with calcium hydroxide under the participation of a hydrolysis auxiliary agent (such as potassium carbonate) to obtain calcium carbonate precipitate and methionine potassium hydrolysate. Separating calcium carbonate from the hydrolysate, concentrating, introducing carbon dioxide to precipitate D, L-methionine, and separating again to obtain D, L-methionine product and crystallized mother liquor containing potassium bicarbonate and a small amount of methionine. And (3) reacting the calcium carbonate taken out after the hydrolysis reaction with the liquid methionine obtained by the previous co-production to prepare the hydroxy methionine calcium to realize autonomous digestion, heating the crystallized mother liquor to convert the crystallized mother liquor into potassium carbonate, circulating the potassium carbonate to the hydantoin hydrolysis step to be used as a hydrolysis auxiliary agent, and not generating inorganic byproduct salt and salt-containing wastewater in the whole D, L-methionine process.
The hydrolysis auxiliary agent has two main functions in the process: firstly, the calcium carbonate is generated by the reaction with calcium hydroxide to release hydroxide radical, so that the conversion of weak base to strong base is realized; secondly, the methionine and potassium ions are ensured to form soluble potassium salt after the reaction is finished, and the loss of the formed methionine calcium along with the precipitation of calcium carbonate is avoided. In addition, the hydrolysis auxiliary agent is not taken out of the system, and the methionine obtained by hydrolysis enters an acidification crystallization step, so that the saturation degree of the generated bicarbonate has great restrictions on the crystallization concentration and the crystallization rate, and therefore, the potassium salt with high solubility is selected. Considering again the synergistic effect with calcium hydroxide, the potassium carbonate normal salt without an acid radical is preferred. After the crystallization mother liquor is circulated, because partial methionine is contained, in order to ensure that hydantoin hydrolysis is completely carried out and good soluble salt is formed, the molar ratio of potassium ions to total hydantoin (hydantoin + methionine) is controlled to be 1-1.2: 1, the molar ratio of calcium hydroxide to hydantoin is controlled to be 0.8-1.2: 1 in order to avoid excessive residues in a system because calcium hydroxide is slightly soluble, and sufficient carbonate (1.3-2 times of the molar equivalent of calcium ions) is added as a cosolvent potassium carbonate in the system to ensure that the calcium ions are precipitated in a calcium carbonate form, so that the influence of the calcium ions on the system and subsequent processes is avoided.
The analytical method of the content of the hydantoin and the methionine is a liquid chromatography or a chemical analytical method, and the specific analytical method is well known by the people in the industry; the method for analyzing the concentration of potassium ions in the cosolvent in the system is ion chromatography or chemical analysis, and the specific method is also well known in the industry.
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
EXAMPLE 1 preparation of cyanohydrin
Transferring 6mol of 99.5% 3-methylthiopropanal into kettle-type or tower-type reactors A and B which are connected in series, respectively adding 10-50 wt% of industrial desalted water and 0.5-5 wt% of citric acid-sodium hydroxide buffer salt catalyst relative to 3-methylthiopropanal, introducing deaminated Anderson hydrogen cyanide gas (HCN content of 7-10 wt%) into a first-stage reaction kettle or tower A (reaction temperature of 20-60 ℃), introducing tail gas after reaction into a second-stage reaction kettle or tower B (reaction temperature of 0-25 ℃) for further absorption reaction, introducing tail gas of the second-stage reactor into a tail gas treatment system, carrying out heat preservation reaction for 1-12 h, carrying out liquid chromatography analysis, obtaining cyanohydrin with the conversion rate of more than 99% in the first-stage reactor, and obtaining a mixture of cyanohydrin and 3-methylthiopropanal with the conversion rate of 20-60% in the second-stage reaction.
Transferring out a cyanohydrin product in the first-stage reactor A to obtain a cyanohydrin aqueous solution product with the conversion rate of more than 99 percent and the cyanohydrin content of 60-90 wt percent. Adding a new raw material for synthesizing the cyanohydrin into the reactor A as a secondary reactor, and connecting the secondary reactor with the reactor B in series to continue the synthesis of the cyanohydrin of the next batch.
EXAMPLE 2 preparation of liquid methionine
Transferring 410g of cyanhydrin (76 wt% in mass fraction) obtained in example 1 into a 316 reaction kettle, adding 0.5-1 molar equivalent of concentrated sulfuric acid (98 wt%) of cyanhydrin, carrying out heat preservation reaction at 30-70 ℃ for 1-5 h to generate hydration reaction of cyanhydrin, carrying out chromatographic analysis on the cyanhydrin conversion, supplementing desalted water, carrying out hydrolysis reaction at 90-130 ℃, carrying out heat preservation reaction for 1-5 h, completing the chromatographic analysis reaction conversion, adding 0.5-1.2 molar equivalent of 30wt% of ammonia water of cyanhydrin, stirring for neutralization for 10-30 min, standing for layering, extracting a water phase, further decompressing and concentrating the oil phase, separating precipitated ammonium sulfate salt, and finally obtaining concentrated liquid methionine solution, and supplementing water to 88-95 wt%.
EXAMPLE 3 preparation of solid methionine
Transferring 390g of cyanhydrin (70 wt% by mass) obtained in example 1 into a zirconium autoclave, adding 1-1.2 molar equivalents of carbon dioxide and 2-2.2 molar equivalents of 20-30 wt% ammonia water, stirring at 140-160 ℃ and 0.5-1.5 MPa (rotation speed of 100-200 r/min), and reacting for 10-60 min to obtain a hydantoin solution. Mixing the obtained hydantoin solution with 0.95-1.2 hydantoin molar equivalent of potassium ions (in the form of potassium carbonate) and 0.8-1.2 hydantoin molar equivalent of calcium hydroxide, transferring into a zirconium material autoclave, stirring at 170-200 ℃ and 0.8-2.0 MPa (rotating speed of 110-300 r/min) for reaction for 10-60 min, hydrolyzing to obtain a hydrolysate and a calcium carbonate precipitate, performing suction filtration to obtain the calcium carbonate precipitate and the hydrolysate, removing dissolved ammonia from the hydrolysate by steam stripping, bubbling, reduced pressure distillation and other modes, concentrating the system until the content of potassium ions is 13-15 wt%, measuring the content of methionine to be 28.2wt%, transferring the hydrolysate to a crystallizer, introducing carbon dioxide at room temperature to neutralize the system until the pH is = 8-9, gradually separating out a large amount of crystals under slow stirring, neutralizing until the pH =8.56 reaches the end point, not reducing the pH value, washing and drying the separated methionine solid to obtain 289.6g, and obtaining the primary extraction rate of methionine to be 81.6%.
The total amount of the obtained crystallization mother liquor (containing washing water) was 980.7g, in which the methionine content was 6.7wt% and the potassium ion content was 8.3 wt%.
EXAMPLE 4 preparation of calcium hydroxy-methionine
The liquid methionine obtained in the embodiment 2 and the calcium carbonate obtained in the embodiment 3 are used as raw materials, the liquid methionine and the calcium carbonate are fed according to the mol ratio of 2-2.2: 1, dilution water (0.5-2 times of the liquid methionine) is added, the mixture reacts for 1-3 hours at the temperature of 70-120 ℃, and hydroxyl methionine calcium and mother liquor are obtained through cooling separation. Drying the hydroxyl methionine calcium at 60-80 ℃ to obtain a finished product, and measuring the calcium: 12.3%, calcium hydroxy methionine (dry basis): 84.4 percent.
The obtained mother liquor is sequentially applied to the next hydroxyl methionine calcium for preparing water supplement.
EXAMPLE 5 Recycling of hydrolysis assistants
The crystallization mother liquor obtained in example 3 (methionine: 6.7wt%, potassium ion: 8.3 wt%) was heated at 100 to 200 ℃ for 20 to 40min to convert potassium ions in the mother liquor from potassium hydrogencarbonate to potassium carbonate, to obtain 245g (methionine: 10.2wt%, potassium ion: 14.2 wt%) of a regenerated mother liquor used as a hydrolysis aid.
The above heating step can also be omitted, and the crystallization mother liquor is directly used as a hydrolysis auxiliary agent for circulation.
The procedure of hydantoin preparation from cyanohydrin as described in example 3 was repeated to obtain 702g of hydantoin solution of 21wt%, and 245g of the above regenerated hydrolysis aid was added thereto, at which time the ratio of potassium ions in the system: total hydantoin (hydantoin + methionine) =0.88:1, 22.7g potassium carbonate was supplemented, making the system potassium ions: adding 74g of calcium hydroxide with the molar equivalent of 0.8-1 hydantoin into the zirconium material reaction kettle, stirring the mixture at the temperature of 170-200 ℃ and the pressure of 0.8-2 MPa (rotating speed of 110-300 r/min) to perform hydrolysis reaction for 10-60 min, separating hydrolysate and calcium carbonate precipitate, allowing the calcium carbonate to enter a calcium hydroxy methionine working procedure, neutralizing and crystallizing the hydrolysate by deamination carbon dioxide to obtain methionine, and continuously circulating the crystallized mother liquor to the next hydrolysis step for use as a hydrolysis aid after direct heating and decarburization.
Particularly, as the circulation times are increased, the crystal extraction rate is gradually stabilized, the regenerated hydrolysis auxiliary agent can gradually provide enough potassium ions to meet the requirement of hydrolysis of a new batch of hydantoin without additionally adding potassium carbonate, and therefore the complicated material feeding calculation work is simplified.
Comparative example 1
Comparative example 3 solid methionine was prepared under the same conditions except that complete potassium carbonate was used for hydrolysis in the hydantoin hydrolysis step, the molar ratio of potassium carbonate to hydantoin was 1-3: 1, the hydrolysate obtained by hydrolysis was deaminated and concentrated to 13-15 wt% of potassium ions, the methionine content in the concentrated hydrolysate was 13-16 wt%, carbon dioxide was introduced at room temperature for neutralization crystallization to obtain methionine solid, the methionine solid was washed and dried to obtain methionine product, the crystal yield was 45-60%, and the obtained crystal mother liquor was 2.02Kg (methionine: 7.28wt%, potassium ions: 7.15wt%).
In conclusion, the method can ensure that the low-added-value byproduct salt is not generated in the process of producing the solid eggs through the co-production of the solid-liquid methionine. The hydrolysis aid potassium carbonate is matched with weak base calcium hydroxide to be used as the hydantoin hydrolysis alkali, so that the hydrolysis aid is more economical than completely using sodium hydroxide, potassium carbonate and other strong bases or salts, the dosage of the hydrolysis aid is only one sixth to one half of that of completely using potassium carbonate to hydrolyze hydantoin, and as can be seen from the comparison between the embodiment 1 and the embodiment 3, the methionine content of the concentrated hydrolysate obtained by the process is 28.2wt% and is far higher than the methionine content of 13-16 wt% of the same potassium ion concentration of the potassium carbonate hydrolysis process. Therefore, the primary crystallization rate is higher, and the amount of the obtained circulating mother liquor is smaller.
Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.
Claims (6)
1. A cleaning process for the co-production of D, L-methionine, D, L-methionine hydroxy analogue and its calcium salt, characterized in that it comprises the following steps:
(1) preparing cyanohydrin: 3-methylthio propionaldehyde and hydrogen cyanide generate 2-hydroxy-4-methylthio butyronitrile, referred to as cyanohydrin for short;
(2) preparing liquid eggs: the cyanohydrin is sequentially subjected to hydration and hydrolysis reaction under the action of acid, and the obtained reaction liquid is neutralized, concentrated and separated by ammonia water to obtain D, L-methionine hydroxyl analogue and a byproduct ammonium salt, wherein the D, L-methionine hydroxyl analogue is short for liquid egg;
(3) preparing a fixed egg: reacting cyanohydrin with carbon dioxide, ammonia gas or ammonium bicarbonate to generate an intermediate 5- (beta-methylthioethyl) hydantoin, and reacting the 5- (beta-methylthioethyl) hydantoin with calcium hydroxide in the presence of a hydrolysis aid to hydrolyze to obtain calcium carbonate precipitate and a D, L-methionine salt solution; separating and removing calcium carbonate in the obtained hydrolysate, concentrating the filtrate, introducing carbon dioxide for crystallization, and separating again to obtain solid D, L-methionine and crystallization mother liquor containing bicarbonate; the 5- (beta-methylmercapto ethyl) hydantoin is abbreviated as hydantoin, and the solid D, L-methionine is abbreviated as solid egg; the hydrolysis auxiliary agent is one or more of sodium hydroxide, sodium bicarbonate, sodium carbonate, potassium bicarbonate or potassium hydroxide;
(4) cross utilization and circulation: reacting the calcium carbonate obtained in the step (3) with the D, L-methionine hydroxy analogue obtained in the step (2) to prepare a D, L-methionine hydroxy analogue calcium salt in a combined manner; and (4) directly recycling the crystallization mother liquor containing the bicarbonate obtained in the step (3) or returning the crystallization mother liquor to the step of hydrolyzing the 5- (beta-methylmercapto ethyl) hydantoin for recycling after heating treatment and decarburization.
2. The process according to claim 1, wherein the catalyst used in the preparation of cyanohydrin from 3-methylthiopropanal and hydrocyanic acid in step (1) is a buffer selected from an aqueous solution of one or more of phosphoric acid and sodium acid phosphate or phosphoric acid and sodium hydroxide, succinic acid and sodium succinate or succinic acid and sodium hydroxide, acetic acid and sodium acetate or acetic acid and sodium hydroxide, citric acid and sodium citrate or citric acid and sodium hydroxide.
3. The process according to claim 1, wherein the acid used in the hydration and hydrolysis of cyanohydrin in step (2) is sulfuric acid, hydrochloric acid or phosphoric acid.
4. The process according to claim 1, wherein the hydrolysis assistant is used in the step (3) in such an amount that the molar ratio of the metal cations of the hydrolysis assistant to the (hydantoin + egg-fixing) is 0.95-1.2: 1.
5. The process according to claim 1, wherein the hydantoin obtained in step (3) is subjected to hydrolysis reaction with calcium hydroxide in the presence of a hydrolysis aid, and the molar ratio of the calcium hydroxide to the hydantoin is 0.8-1.2: 1.
6. The process according to claim 1, characterized in that the specific separation operation of the calcium carbonate and the hydrolysate in the step (3) is suction filtration, pressure filtration or centrifugation; and the separation operation of the solid D, L-methionine crystal and the mother liquor is suction filtration, filter pressing or centrifugation.
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| CN110577479A (en) * | 2019-09-25 | 2019-12-17 | 福安药业集团重庆博圣制药有限公司 | Novel crystal form A of racemic hydroxy methionine calcium and preparation method and application thereof |
| CN112679398A (en) * | 2020-12-21 | 2021-04-20 | 宁夏紫光天化蛋氨酸有限责任公司 | Post-treatment method of saponification liquid of DL-methionine |
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| DE19547236A1 (en) * | 1995-12-18 | 1997-07-03 | Degussa | Process for the preparation of D, L-methionine or its salt |
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